1. Field of the Invention
This invention relates to material for sealing threaded pipe joints, particularly for use in the plumbing industry for making joints in pipes for water-supply, water-discharge, heating and the like, but also having utility for other types of pipework, e.g., in industrial plants. The invention also relates to a dispenser for the material.
2. Brief Description of the Related Technology
It is well known for plumbers to use a two-part system of hemp fibre and paste for sealing threaded pipe fittings. Dry hemp fibre is usually supplied in loose unwoven form, and a quantity is taken and drawn out into a length. Hemp is also available in the form of a hank wound on a spool which can be held in a dispenser with a tubular dispensing guide for the hemp. In either case, a length of hemp is wrapped around the threaded area of a male pipe fitting. The paste may be applied to the fitting first, in which case the hemp is drawn through the paste as it is wrapped around the fitting, or alternatively (or in addition) the paste is applied over the hemp. The paste keeps the hemp in place on the male threaded fitting. The female threaded fitting is then applied and completes the joint. The joint can be adjusted later, if desired.
While this two-part system is widely used, it is not acceptable for pipes intended to carry drinking water because hemp does not meet the standards for materials in contact with potable water. Hemp is capable of supporting microbiological growth.
An alternative two-part system is available using polypropylene fibre instead of hemp, which system is approved for contact with potable water. However any two-part system has disadvantages because it is cumbersome to use and requires a high degree of skill and takes time to apply.
Another commercially available sealing material is a polytetrafluoroethylene (“PTFE”) tape which is non-fibrous in nature. It is typically about 10 mm wide and 0.25–0.5 mm thick. In use, the tape is wound around the threaded area of a male fitting, with a number of overlaps used to build up a thickness as desired. The female threaded part is then applied to complete the assembly. This system also requires skill in application and it suffers the disadvantage that it cannot be used in a joint where readjustment may be necessary without loss in seal.
Georg Fischer Rohrverbindungstechnik GmbH of D-78224 Singen, Germany, offers for sale a range of The cap materials including pastes for use with hemp and also including a product called PARALIQ PM 35 VLIES which comprises a tape in the form of a synthetic special web, fleece or gauze saturated with a thread sealing paste. It is fibrous in nature like hemp and can be used without either hemp or a separate paste. The tape is 16 mm wide and is available in a roll of tape 10 m or 25 m long. The 25 m tape is said to be sufficient for 100 1 inch (25 mm) threads (i.e. threads on pipe of 1 inch (25 mm) outside diameter). The broad tape is less convenient for the plumber to handle than fibrous hemp or a yarn. It is applied across a number of threads in a band 16 mm wide rather than being wound into individual threads. It is supplied on a roll but not in a dispenser which can be handled by the plumber in one hand.
In a different technical field, dental floss is available in the form of a multifilament yarn, optionally waxed, which is wound on a spool and held in a dispenser with a dispensing aperture. A blade for cutting the yarn is located on the exterior of the dispenser, adjacent to the dispensing aperture, for cutting the yarn into desired lengths. Dental floss is not (1) a sealing material or (2) coated with a composition suitable for sealing pipe joints. Accordingly, dental floss does not provide teaching relevant to the field of threaded pipe joints.